<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>比赛中的配对次数</title>
</head>
<body>
  <script>
    function fn(n) {
      return n - 1
    }
    console.log(fn(7))
  </script>
</body>
</html>